Among methods of obtaining colored glass is the ion exchange method in which a glass surface is coated with an inorganic salt of silver or an inorganic salt of copper and then baked to cause the silver or copper micro-particles in the inorganic salt to permeate into the glass substrate and thus cause colloidal coloration of glass to occur. There is also a method in which a salt of gold, silver, or other metal is dissolved in a silicon alkoxide solution, the resulting solution is coated onto the substrate, and heat treatment is performed to form a silicon oxide coating containing metal micro-particles.
In particular, glass which has been colored by the surface plasmon of gold or silver micro-particles excels in heat and light resistance and has been used priorly as colored glass or filter glass. In recent years, the sol-gel method has come to be used widely. For example, a method of providing a colored film coated glass plate is described in J. Sol-Gel. Sci. Techn. 1, 305-312 (1994) in which a glass substrate is coated with a solution containing chloroauric acid and alkoxide of silane and then subject to heat treatment to form a silica film as a matrix containing gold micro-particles in the dispersed condition.
However, in obtaining a gold micro-particle dispersion colored film coated glass by the sol-gel method, there was a problem in that in the abovementioned process of heat treatment of the film, the growth of gold micro-particles occurs at the same time as the contraction of the matrix and the gold micro-particles thus tended to become expelled outside of the film. Since the expelled gold micro-particles come off readily when the film is wiped with the hands, the proportion of chloroauric acid in the coating solution that remains as gold micro-particles in the colored film is decreased and the coloring effect is weakened. Also in the actual mass production process, the amount of micro-particles that are expelled outside of the film varies and this has been a factor of variation of the quality of colored glass and has lead to a lowering of yield and increases in cost.
The object of the present invention is to present a colored film forming composition, with which the precipitation of gold micro-particles on the film surface is prevented and gold micro-particle dispersion glass can be manufactured in a stable manner by the sol-gel method, and a method of manufacturing a colored film coated glass product using the colored film forming composition.